1. Field of the Invention
The present invention is directed to a method of determination of a three-dimensional profile of an object in accordance with the concept of triangulation, and a device for determining the same.
2. Description of the Prior Art
In the past, a device for determining a three-dimensional profile of an object surface is utilized in inspection systems or industrial robots, etc. For example, Japanese Patent Publication [KOKOKU] 4-7806 presents an optical measurement system. As shown in FIG. 23, the system includes a light projecting device 2L for simultaneously emitting light beams to an object surface 1L to obtain a plurality of light spots LS on the object surface 1L, a video camera 3L spaced by a distance from the projecting device 2L for monitoring the light spots LS, and a computer (not shown) for operating positional data provided from the video camera 3L. In the prior art, when one of the light beams forms a light spot on the object surface, the light spot is monitored to form an object spot on a screen of the video camera 3L. On the other hand, when the same light beam forms an imaginal light spot on an imaginal surface spaced by the already known distance from the video camera 3L, a reference spot corresponding to the imaginal light spot is also formed on the screen of the video camera 3L. By analyzing a positional deviation between the object spot and the reference spot, a positional data of the object surface is obtained. The three-dimensional profile of the object is determined by collecting the positional data with respect to all light spots simultaneously projected on the object surface.
However, if some light spots are formed on a view line extending between the video camera 3L and a point on the 10 object surface, there is a problem that it is very difficult to distinguish one of the light spots from the another light spots, so that the three-dimensional profile of the object is not accurately obtained. Moreover, since this prior measurement system uses the video camera, there has a technical difficulty of detecting positional data from a wide surface area of the object.
On the other hand, U.S. Pat. No. 5,102,226 discloses a position detector utilized in an optical measurement system for determination of an object profile. As shown in FIG. 24, the position detector has a number of light receiving elements 40M.sub.0 to 40M.sub.7 arranged in two linear arrays 20M consisting of first and second arrays 21M and 22M extending in the direction of following a reflected light beam from the object surface as a scan angle of a light beam varies. In addition, each array is divided into eight subdivisions. That is, the receiving elements 40M.sub.0 to 40M.sub.7 in the first array 21M are designated by eight numerals "0" to "7", wherein one subdivision of the first array 21M consists of eight receiving elements with the same numeral, but has different numeral from another subdivisions. On the other hand, the receiving elements 40M.sub.0 to 40M.sub.7 in the second array 22M are grouped in such a manner that each subdivision consists of the receiving elements with eight different numerals "0" to "7". For instance, when the reflected light beam is focused on the linear arrays to form the beam spot LS at the illustrated position in FIG. 23, a coded signal "56" is issued as a result of that one of photo detectors 10M.sub.0 to 10M.sub.7 associated with the first array 21M through optical fibers 30M responds to provide a first output indicative of numeral "5" and one of photo detectors 11M.sub.0 to 11M.sub.7 associated with the second array 22M through the optical fibers 30M provides a second output indicative of numeral "6". The coded signal is stored as a positional data with respect to the object surface. The receiving elements of thus arranged arrays provides a resolution of 64 (8.times. 8) spots.
Accordingly, in case of determining the three-dimensional profile of the object with this prior system, as long as the light beam is scanned on a flat surface, the light beam reflected from the flat surface strikes the position detector at the same beam spot on the first and second arrays. When the light beam is scanned onto a convex or concave surface of the object which provides a positional deviation in a direction perpendicular to the flat surface, the light beam reflected from the object surface strikes the position detector at a different position from the beam spot obtained with respect to the flat surface. By detecting the beam spots with respect to individual points obtained by scanning the light beam onto the object surface, the three-dimensional profile of the object is accurately determined.
However, in this prior art, since it is required that a oscillating mirror for redirecting the reflected light beam from the object to the position detector is oscillated in synchronism with the other oscillating mirror for scanning the light beam on the object surface, such an optical measurement system creates difficulties because of necessary complex mirror synchronizing means and its expensive cost.
Moreover, when a plural number of the position detectors are used to obtain positional data from the wide surface area of the object, there has also problem of increasing the expensive photo detectors 10M.sub.0 to 10M.sub.7 and 11M.sub.0 to 11M.sub.7.